Thermal, or infrared (IR), images of scenes are often useful for monitoring, inspection and/or maintenance purposes, e.g. for monitoring gas leaks at an industrial plant. Typically, a thermal imaging device, e.g. in the form of a thermography arrangement or an infrared IR camera, is provided to capture infrared (IR) image data values, representing infrared radiation emitted from an observed scene. The captured IR image can after capturing be processed, displayed and/or saved, for example in the thermal imaging device or in a computing device connected to the thermal imaging device such as a tablet computer, a smartphone, a laptop or a desktop computer.
Thermal imaging devices, such as IR cameras, might be used for detecting gas occurrence, for example in the form of a gas cloud or gas plume e.g. from fugitive gas emissions or gas leaks, and for producing a visual representation of such gas occurrence as a gas image. Such a gas image can be used for visualizing gas occurrence or gas leaks, e.g. as smoke or a cloud on images presented on the viewfinder of a camera, on an integrated or separate display, or on an external computing device, thereby allowing the user to see gas occurrence in a scene observed and imaged by means of an IR camera. A variant of such techniques is called passive infrared gas imaging and is based on using radiation from a scene without any additional illumination for detecting gas.
However, a problem with conventional systems is that the sensitivity of the thermal imaging device might be too low to detect gas below a certain gas particle concentration or, in other words, the contrast between gas information and noise/interference in a generated gas image is too low to identify gas. Another problem is that the sensitivity is further reduced by various physical aspects, such as varying temperatures and emissivity in the observed scene background, noise, other gases, aerosol particles and moving gas clouds.
In conventional technology, particularly using cooled thermal imaging devices, gas imaging may be based on the difference in absorption or transmission of infrared radiation in different wavelength bands. A problem, particularly with uncooled thermal imaging devices, is that when basing gas imaging on the difference in absorption or transmission of infrared radiation in selected wavelength bands, the bands cannot be made narrow due to high noise contribution by imaging device components such as filters, optical systems, wave guide and the detector itself. This means that physical characteristics of the system, such as noise or thermal interference might vary significantly with wavelength and will be more difficult to compensate for.
In conventional systems, particularly using cooled thermal imaging devices, gas imaging may be based on the difference in absorption or transmission of infrared radiation in different wavelength bands. A problem, particularly with uncooled thermal imaging devices, is that when basing gas imaging on the difference in absorption or transmission of infrared radiation in selected wavelength bands, the sensitivity of the thermal imaging device might be too low to quantify gas below a certain gas concentration or in other words the contrast between gas information and noise/interference in a generated gas infrared image is too low to quantify gas.
Therefore, there is a need to address the problems of conventional systems to improve quantify gas in passive imaging.